It is common practice to supply medical solutions for parenteral administration in the form of disposable, flexible pouches. One class of such pouches is commonly referred to as an “I.V. bag.” These pouches must meet a number of performance criteria, including collapsibility, optical clarity and transparency, high-temperature heat-resistance, and sufficient mechanical strength to withstand the rigors of the environment in which they are used. Medical solution pouches should also provide a sufficient barrier to the passage of moisture vapor and other gasses to prevent contamination of the solution contained therein.
High-temperature heat resistance of medical pouches is important so that the contents of the pouch can be heat sterilized. Heat-sterilization of solution-containing medical pouches typically occurs in an autoclave at about 250° F. for periods of 15 to 30 minutes. Steam is generally used as the heat-transfer medium. Heat-sterilization is normally performed by the manufacturer and/or packager of the medical solution prior to sending the packaged medical solution to the end user, e.g., a hospital. This helps to ensure that the medical solution, as packaged in the medical solution pouch, will be substantially free from contamination. Accordingly, a requirement of medical solution pouches is that they must be able to endure the high temperatures which are encountered during heat-sterilization without deterioration by, e.g., developing a heat-seal leak or other type of containment failure.
To achieve the desired properties and functionalities, films for use in medical pouch applications generally include multiple layers in which each layer provides one or more properties so that the resulting pouch has the desired end properties. For example, the film may include outer layers and one or more inner layers including adhesive or “tie” layers that adhere layers to each other. Generally, films for use in the preparation of medical pouches include a heat/abuse-resistant layer that forms the outside surface of the pouch. The primary functions of the outer layer are to provide heat-resistance to the pouch during heat-sealing and heat-sterilization, and to provide abuse-resistance from external handling and abrasion.
During autoclaving, the film is subjected to a high temperature to sterilize the contents of the pouch. In the case of medical solutions, the autoclaving process can result in the formation of bubbles or foam within the solution. It is believed that the formation of bubbles or foam may be the result of components of the film that have migrated into the medical solution during autoclaving. The presence of such foam/bubbles may in some cases be undesirable. For instance, films for use in medical pouches in China must pass a so-called “bubble test” in which the presence of any bubbles or foam after autoclaving and rigorous shaking must quickly dissipate.
Accordingly, there exists a need for a multilayer film that is suitable for as a material for the manufacture of medical solution pouches, and which has a reduced proficiency for forming foam or bubbles after the pouch has been heat-sterilized.